The Supreme Court on Friday limited the ability of lower-court judges to block executive branch policies nationwide, opening the door for a majority of states to at least temporarily enforce President Donald Trump’s executive order ending birthright citizenship.

With their decision, the justices appeared to upend the ability of single federal judges to freeze policies across the country. The powerful legal tool, known as a nationwide injunction, had been used frequently in recent years to block policies put in place by Democratic and Republican administrations and gave rise to charges of judge shopping.

But the immediate effect of the 6-3 decision, which was written by Justice Amy Coney Barrett and split along ideological lines, was to give Trump a major if perhaps temporary victory in his efforts to redefine citizenship in the United States.

The justices did not rule on the constitutionality of the executive order issued by Trump in January, which seeks to end the practice of automatically granting citizenship to anyone born in the United States, even if the parents are not citizens. That question is likely to come back to the Supreme Court, perhaps as soon as next year.

In the meantime, the decision cleared the way for the executive order to go into effect in the 28 states that have not challenged it, which could create a patchwork system in which the rules for citizenship are different in different parts of the country.

Still, the Supreme Court ruling will not take effect for 30 days. And the justices laid out a potential path for challengers, saying that district court judges could consider whether to take up class-action suits seeking to bar enforcement of the executive order on a statewide, regional or even national basis.

Indeed, groups challenging the executive order immediately seized on that opening, with class-action filings in Maryland and New Hampshire. Other challengers are likely to do the same in the coming days.During its first few months, the Trump administration has seen its efforts to enact its sweeping policy agenda stymied by federal trial court judges who wielded nationwide injunctions that blocked the government at every turn.

Trump began his second term by signing a flurry of executive orders, including declaring an end to birthright citizenship, but many were immediately paused by trial courts. In response, Trump and his allies have for months publicly attacked trial court judges who ruled against the administration, claiming the judges had exceeded their power.

The administration repeatedly challenged many of the nationwide injunctions, seeking emergency relief from the Supreme Court.

At a news conference after the court’s decision, Trump appeared triumphant.

“Our country should be very proud of the Supreme Court today,” he said.

Calling the justices’ decision “giant,” Trump said his administration would quickly move to put in place policies that were blocked by nationwide injunctions, including his birthright citizenship policy.

Legal experts predicted that the ruling was likely to set off a flood of individual lawsuits and requests for class actions in other matters, with the ultimate impact on the Trump agenda unclear. Regardless, they said it would leave the power of the presidency greatly expanded.

“Boy, is there now an incentive to just do whatever you want,” said Amanda Frost, a law professor at the University of Virginia. “It really ties the hands of the judiciary to keep the executive in line.”

Sen. Chuck Schumer, D-N.Y., the minority leader, warned that the court’s decision was a “terrifying step toward authoritarianism” and urged Congress to fill what he viewed as the void left by the judiciary to check the power of an out-of-control executive branch.

“Republican members must stand up for core American democratic values and not for unchecked presidential power of the kind that our founders most deeply feared,” he said in a statement.

Legal advocacy groups that have been active in fighting the Trump administration’s most sweeping policies vowed to find workarounds, including class-action lawsuits and parallel challenges across multiple federal districts, if necessary.

“A number of pathways remain for individuals to obtain relief from the courts,” Skye Perryman, president of Democracy Forward, said in a statement. She called the ruling “disappointing and yet another obstacle” to protecting constitutional rights.

The practice of automatically granting citizenship to children born on American soil is rooted in the 14th Amendment. Ratified after the Civil War, the amendment, which extended citizenship to Black Americans, was part of an attempt to block the Confederate states from denying civil rights to former slaves.

The first sentence of the amendment declares that “all persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside.”

In 1898, the Supreme Court affirmed that right in a landmark case, United States v. Wong Kim Ark. For more than a century, courts have upheld that interpretation.

While the executive order was blocked, the Trump administration provided no details about how it would go about carrying out a wholesale change in how the nation grants citizenship.

In the opinion, Barrett explained the majority’s view that nationwide blocks by federal judges “likely exceed” their authority because such injunctions allowed judges to freeze a policy for everyone in the country, rather than just those involved directly in a court case.

Barrett cited examples of several justices criticizing nationwide injunctions and quoted an influential law review article that argued that by the end of the Biden administration, nearly every major presidential act had been immediately blocked by a federal trial judge.

She said that such nationwide freezes were a relatively recent phenomenon, a legal tool that was “conspicuously nonexistent for most of our nation’s history.”

A move by the presidency to overstep does not give the courts permission to abuse their power, Barrett wrote.